Abstract [en]

Providing broadband in-flight Internet connectivity to aircraft is challenging. Today's options include satellite communications (SC) and direct air-to-ground communication (DA2GC). To overcome data rate, delay and cost limitations of SC and coverage limitations of DA2GC, one can extend DA2GC with air-to-air communication (A2AC) by enabling multi-hop communication. To investigate the A2AC performance, we construct a mixed integer linear programming (MILP) problem of DA2GC and A2AC, jointly considering interference in topology formation and flow assignment. Our objective is to maximize the number of aircraft that can be connected with a given specific minimum data rate threshold. The evaluation is performed for low aircraft density scenarios over the North Atlantic. We show that in the investigated scenarios, over 90 % of aircraft can have at least 50 Mbps, some being up to 1600 kilometers away from the closest base station (BS). Furthermore, we identify antenna capabilities as an important factor for A2AC performance.

Abstract [en]

In this paper, we study cross-layer optimization of low-power wireless links for reliability-aware applications while considering both the constraints and the nonideal characteristics of the hardware in Internet-of-Things (IoT) devices. Specifically, we define an energy consumption (EC) model that captures the energy cost-of transceiver circuitry, power amplifier (PA), packet error statistics, packet overhead, etc.-in delivering a useful data bit. We derive the EC models for an ideal and two realistic nonlinear PA models. To incorporate packet error statistics, we develop a simple, in the form of elementary functions, and accurate closed-form packet error rate approximation in Rayleigh block-fading. Using the EC models, we derive energy-optimal yet reliability and hardware compliant conditions for limiting unconstrained optimal signal-to-noise ratio (SNR), and payload size. Together with these conditions, we develop a semianalytic algorithm for resource-constrained IoT devices to jointly optimize parameters on physical (modulation size, SNR) and medium access control (payload size and the number of retransmissions) layers in relation to link distance. Our results show that despite reliability constraints, the common notion-higherorder M-ary modulations are energy optimal for short-range communication-prevails, and can provide up to 180% lifetime extension as compared to often used OQPSK modulation in IoT devices. However, the reliability constraints reduce both their range and the energy efficiency, while nonideal traditional PA reduces the range further by 50% and diminishes the energy gains unless a better PA is used.

Abstract [en]

The heated 5G network deployment race has already begun with the rapid progress in standardization efforts, backed by the current market availability of 5G-enabled network equipment, ongoing 5G spectrum auctions, early launching of non-standalone 5G network services in a few countries, among others. In this article, we study current and future wireless networks from the viewpoint of energy efficiency (EE) and sustainability to meet the planned network and service evolution towards, along, and beyond 5G, as also inspired by the findings of the EU Celtic-Plus SooGREEN Project. We highlight the opportunities seized by the project efforts to enable and enrich this green nature of the network as compared to existing technologies. In specific, we present innovative means proposed in SooGREEN to monitor and evaluate EE in 5G networks and beyond. Further solutions are presented to reduce energy consumption and carbon footprint in the different network segments. The latter spans proposed virtualized/cloud architectures, efficient polar coding for fronthauling, mobile network powering via renewable energy and smart grid integration, passive cooling, smart sleeping modes in indoor systems, among others. Finally, we shed light on the open opportunities yet to be investigated and leveraged in future developments.

Abstract [en]

There is an increasing demand for in-flight broadband connectivity. Some airlines are already deployed satellite-based solutions, which have low data rate and high latency. In order to tackle these problems, direct air-to-ground communication (DA2GC), where a direct link between a ground station and an airplane is established, is a promising solution. The resource utilization in DA2GC systems can be enhanced with the introduction of multi-user beamforming techniques, where each airplane has its dedicated beam and exploits a larger portion of the spectrum available to DA2GC. Even with multiuser beamforming technique, some airplanes may experience low data rates due to interference caused by beams aimed at airplanes in the mutual vicinity. The probability that two or more beams will interfere is higher with longer inter-site distance or wider beamwidth, which is often the case for DA2GC systems. To address significant research problem, we propose a coordinated resource allocation scheme with beam selection and spectrum allocation. The proposed beam selection scheme coordinates the neighboring base stations such that the number of airplanes sharing the same beam is minimized. In addition, the proposed coordinated spectrum allocation scheme maximizes the minimum amount of spectrum dedicated for each airplane. According to our results, the proposed coordinated beam selection with efficient spectrum allocation improves average capacity available per airplane by 60% in comparison with the uncoordinated scheme.

Schupke, Dominic

Abstract [en]

The wireless communications finds many applications inside an aircraft cabin, in terms of Passenger and Crew Communications as well as Machine Type Communications (MTC). The aircraft cabin is a challenging environment and the different wireless technologies must be adequately tested and adapted to achieve maximum performance. In this regard, an aircraft environment has been analyzed in this paper for an in-cabin wireless system implementation and the measurement results have been further evaluated. This is an integrated system for the technologies of LTE, LAA and NB-IoT for the potential use-cases of Passenger Connectivity, On-Board Sensing, Cargo Tracking and Passenger Announcement. Results have then been summarized within the scope of this paper.

Abstract [en]

Massive MIMO (MM) is one of the leading technologies that can cater for very high capacity demand. However, energy consumption of MM systems needs to be load adaptive in order to cope with the significant temporal load variations (TLV) over a day. In this paper, we propose a game-theoretic model for studying load adaptive multicell massive MIMO system where each base station (BS) adapts the number of antennas to the TLV in order to maximize the downlink energy efficiency (EE). The utility function considered here is defined as the number of bits transferred per Joule of energy. In order to incorporate the TLV, the load at each BS is modeled as an M/G/m/m state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at the peak load. The EE maximization problem is formulated in a game theoretic framework where the number of antennas to be used by a BS is determined through the best response iteration. This load adaptive system achieves around 24% higher EE and saves around 40% energy compared to a baseline system where the BSs always run with the fixed number of antennas that is most energy efficient at the peak load and that can be switched OFF when there is no traffic.

Abstract [en]

IoT networks with grant-free radio access, like SigFox and LoRa, offer low-cost durable communications over unlicensed band. These networks are becoming more and more popular due to the ever-increasing need for ultra durable, in terms of battery lifetime, IoT networks. Most studies evaluate the system performance assuming single radio access technology deployment. In this paper, we study the impact of coexisting competing radio access technologies on the system performance. Considering K technologies, defined by time and frequency activity factors, bandwidth, and power, which share a set of radio resources, we derive closed-form expressions for the successful transmission probability, expected battery lifetime, and experienced delay as a function of distance to the serving access point. Our analytical model, which is validated by simulation results, provides a tool to evaluate the coexistence scenarios and analyze how introduction of a new coexisting technology may degrade the system performance in terms of success probability and battery lifetime. We further investigate solutions in which this destructive effect could be compensated, e.g., by densifying the network to a certain extent and utilizing joint reception.

Cavdar, Cicek

Abstract [en]

IoT networks with grant-free radio access, likeSigFox and LoRa, offer low-cost durable communications overunlicensed band. These networks are becoming more and morepopular due to the ever-increasing need for ultra durable, interms of battery lifetime, IoT networks. Most studies evaluatethe system performance assuming single radio access technologydeployment. In this paper, we study the impact of coexistingcompeting radio access technologies on the system performance.Considering K technologies, defined by time and frequencyactivity factors, bandwidth, and power, which share a set of radioresources, we derive closed-form expressions for the successfultransmission probability, expected battery lifetime, and experienceddelay as a function of distance to the serving access point.Our analytical model, which is validated by simulation results,provides a tool to evaluate the coexistence scenarios and analyzehow introduction of a new coexisting technology may degrade thesystem performance in terms of success probability and batterylifetime. We further investigate solutions in which this destructiveeffect could be compensated, e.g., by densifying the network toa certain extent and utilizing joint reception.

Abstract [en]

The rising number of airplanes and UAVs requiring connectivity in the sky puts high demands on all types of networks. In areas without DA2GC coverage, such as sea or oceans, the only option is SC. However, the capacity of SC is limited and insufficient in some cases. Therefore, an extension of DA2GC by A2AC and integration of A2AC and SC is a promising solution to improve available capacity. The main aim of this article is to evaluate limits of SC and A2AC in terms of maximum available capacity and maximum range. The results show that A2AC through DA2GC backhauling is able to overcome capacity available by SC on certain conditions while flying close to the mainland. Integration of A2AC and SC can significantly improve data rate available for UAVs and airplanes, especially if the sky cannot be covered by DA2GC only. Our results show that A2AC can provide capacity up to 93 Mb/s, and it can even exceed the capacity of SC when DA2GC and A2AC distances are short. When SC is overloaded, A2AC can be used instead to provide airplanes with capacity of 37 Mb/s up to 432 km DA2GC distance and 340 km A2AC distance. Besides the evaluation of both networks, the article also summarizes and discusses potential challenges and open issues of integration that need to be considered on the way to successful cooperation of both networks.

Abstract [en]

Leveraging grant-free radio access for enabling low-power wide-area (LPWA) Internet of Things (IoT) connectivity has attracted lots of attention in recent years. Regarding lack of research on LPWA IoT networks, this work is devoted to reliability modeling, battery-lifetime analysis, and operation-control of such networks. We derive the interplay amongst density of the access points, communication bandwidth, volume of traffic from heterogeneous sources, and quality of service (QoS) in communications. The presented analytical framework comprises modeling of interference from heterogeneous sources with correlated deployment locations and time-frequency asynchronous radio-resource usage patterns. The derived expressions represent the operation regions and rates in which, energy and cost resources of devices and the access network, respectively, could be traded to achieve a given level of QoS in communications. For example, our expressions indicate the expected increase in QoS by increasing number of transmitted replicas, transmit power, density of the access points, and communication bandwidth. Our results further shed light on scalability of such networks and figure out the bounds up to which, scaling resources can compensate the increase in traffic volume and QoS demand. Finally, we present an energy-optimized operation control policy for IoT devices. The simulation results confirm tightness of the derived analytical expressions, and indicate usefulness of them in planning and operation control of IoT networks.